The present invention relates to a tracking and driving speed regulating device for motor vehicles, having a sensor device for monitoring a road track, a steering regulator for analyzing signals of the sensor device and for issuing steering commands to a steering actuator, and having a cruise controller, acting upon the drive system of the vehicle, which can be switched to an operational state using a main switch, and, in the operational state, may be activated by an actuation signal generated by an operating element
Vehicle speed regulating devices for motor vehicles are known, with which the speed of the vehicle is held to a setpoint value set by the driver. By operating the main switch, the cruise control is converted to the operational state. The actual cruise control, however, begins only when the driver gives a so-called set command by using an operating element, typically a multifunctional switch designed as a lever which is positioned near the steering wheel. This command has the effect that the actual speed of the vehicle is assumed as the setpoint value and put in as the basis for the cruise control.
The input of the set command usually takes place by deflecting the multifunctional switch briefly in the direction (setxe2x88x92). Prolonged holding of the multifunctional switch in the (setxe2x88x92) position has the effect of throttling the vehicle engine and gradually decreasing the speed. As setpoint value for the subsequent cruise control, the speed is then taken over which the vehicle had reached when the switch was let go. As a matter of choice, cruise control can also be activated by deflecting the multifunctional switch briefly in the opposite direction (set+). Prolonged holding of the multifunctional switch in the (set+) position has the effect of increasing the setpoint value, and thus accelerating the vehicle. In this case, too, the speed reached by the vehicle, when the switch is let go, forms the setpoint value for the subsequent regulation. By inputting the command xe2x80x9ccancelxe2x80x9d the cruise controller is inactivated. However, the most recently valid setpoint value remains stored. By inputting the command xe2x80x9cresumexe2x80x9d the cruise controller can be reactivated, so that cruise control to the previously stored setpoint value can be resumed. Input of the commands xe2x80x9ccancelxe2x80x9d and xe2x80x9cresumexe2x80x9d is usually performed by pulling or pushing the multifunctional switch in the direction at right angles to the directions xe2x80x9csetxe2x88x92xe2x80x9d and xe2x80x9cset+xe2x80x9d. By switching off the main switch, the regulating system is completely inactivated, and the stored setpoint value is deleted.
A further development of this cruise control system, also known as xe2x80x9ccruise controlxe2x80x9d, is represented by so-called adaptive cruise control (ACC). In such an ACC system, using a radar device, the distance from a preceding vehicle is additionally measured, and, provided there is a vehicle within the detection range of the radar, the regulation is not made based on the preset setpoint speed but rather based on a safe, speed-dependent setpoint distance from the preceding vehicle. Examples of such ACC systems, the use of which can considerably increase travel comfort and safety, are described in German Published Patent Application No. 42 00 694, as well as in Winner et al.: xe2x80x9cAdaptive Cruise Control System Aspects and Development Trendsxe2x80x9d, SAE Technical Paper Series 96 1010, 1996, pp 27-36. In these systems it is provided that the regulation of the separation distance is interrupted if the driver intervenes in the driving happenings, for example, by activating the brake.
German Published Patent Application No. 195 07 957 proposes a tracking and travel speed regulating device, which supports the driver not only in keeping to the desired speed and/or the distance from the preceding vehicle, but also in keeping in lane (LKS=lane keeping support). An optical sensor device is provided for this, with the use of which the spatial position of the vehicle with respect to the lane can be detected, for example, by the use of lane markings. If electronic evaluation of the data detected, using the optical sensor device, indicates that the vehicle is approaching a lateral lane limit, an intervention in the steering of the vehicle is made in such a way that the vehicle is drawn into the middle of the lane. As mentioned in the cited document, this automatic tracking function can be activated and deactivated by the driver in a similar manner, as is the case in the vehicle speed regulating device described at the outset. This tracking function is also automatically deactivated when the driver operates the brake or otherwise actively intervenes in the travel happenings. To be sure, a desirable unloading of the driver is achieved by these various types of automated functions, but on the other hand, along with the increasing number of automated functions, there is also an increase in the appertaining operating elements as well as the number of possible combinations of system states, and it is becoming increasingly more difficult for the driver to keep current at all times on the active or inactive state of the systems or partial systems. In some individual cases this may lead to misestimations or to irritations which impair the driver""s sense of safety, and thus also of the acceptance of such automatic support systems.
It is the object of the present invention to create a tracking and driving speed regulating device which makes a simpler and more lucid operation possible for the driver.
According to the present invention, the object is attained by making the steering regulator switchable to an operating state by a separate main switch independent of the speed regulator, and being able to be activated in the operating state by the same actuation signal as the speed regulator.
Although the cruise control (ACC), on the one hand, and the steering control (LKS), on the other hand, fundamentally work independently of each other, according to the present invention, both systems are activated by the same actuation signal, so that a common operating element can be used for producing this actuation signal. In this way, not only is a structural simplification achieved by simplification of the number of operating elements, but, above all, the clarity of the operating system is improved. Yet, the separate main switches make it possible to switch the two systems on and off separately of each other, so that the driver keeps the unlimited freedom of decision on whether, and possibly which of the available functions he wants to use.
However, in the case of regulation, under the conditions under which the automatic tracking function can be used in a way that makes sense (clearly marked lanes, no crossings, off ramps or sharp curves), suitable assumptions for using the cruise control or (inter-automobile) separation regulating function may be in order. This is true particularly in the case of travel on expressways or country roads having few curves. In practice, therefore, the two automatic functions ACC and LKS are mostly used together, and under these circumstances, the possibility of activating both systems by using a single command represents a clear improvement in operating comfort. In a typical application, for example, the case of an express highway trip, after accessing the expressway, the driver has to operate the main switch for both systems only once. Then, during the trip, if, for example, both automatic functions were interrupted because of a braking maneuver, one single command, which produces the actuation signal, ensures that both systems are reactivated again, and for example, a situation is avoided where the driver does indeed reactivate the separation distance regulation, but forgets to reactivate the tracking function as well, and then notes with alarm that the vehicle runs out of the lane.
As a matter of preference, the cruise control and the automatic tracking function can also be deactivated by at least one common switch-off signal. An example of such a common switch-off signal is the signal indicated by the operation of the vehicle brakes. It is also expedient to generate a common switch-off signal when the vehicle speed falls below a certain value, such as 40 km/h, below which neither the automatic speed or separation distance regulation nor the automatic tracking function is meaningful. In vehicles having standard shift, operation of the clutch pedal can also trigger a common switch-off signal.
The xe2x80x9ccancelxe2x80x9d command, by which the speed or separation distance regulation is deactivated, can also be used for deactivating the tracking function. If the constellation of signals leading to the deactivating of the speed or separation distance regulation system is identical to the constellation of signals leading to the deactivating of the tracking function, then the advantage is that the activating conditions are consistent to the driver, that means, he can rely on the fact that, as long as both main switches are switched on, the tracking function is active when, and only when the cruise control function is also active, and vice versa.
In another embodiment, however, special exceptional conditions can be determined, under which the speed and separation distance regulating function on the one hand, and the tracking function on the other hand, can be deactivated independently of each other, so as to take into account special traffic situations. An example of this would be a situation in which the vehicle is proceeding in the left lane of the expressway and the driver ascertains that, far ahead of him, a truck is veering out to overtake somebody. Even if the truck is not yet within radar range, a far-sighted driver will cut his speed early. This can actually be done by the command xe2x80x9csetxe2x88x92xe2x80x9d, without deactivating the regulating systems, but in that case, the multifunctional switch should be held for a prolonged period. Therefore, many drivers prefer giving the command xe2x80x9ccancelxe2x80x9d to let the vehicle continue to coast until a suitable, lower setpoint speed has been reached. Under these conditions there is no need for also deactivating the tracking function while the vehicle coasts. Something similar applies when the driver wishes to drop further back from the preceding vehicle, in order to permit a traffic participant driving in front of him, to the right, the possibility of cutting into the left lane. One can take account of these situations by additionally making deactivation of the tracking function dependent on the driver""s actively operating the gas pedal and/or intervening in the steering, and thereby letting it be known that he himself wants to assume sole control.
As opposed to this, there are also situations in which the tracking function should be at least briefly deactivated while cruise control remains active. An example would be the case in which the vehicle is approaching a slower preceding vehicle in the right lane. As long as the left lane is free, he will then make a move to pass, without changing speed. The intention of changing lanes can be recognized in this case, for example, by setting the turn signal.
In the ACC system, special-case strategies can be implemented which permit, within certain limits, a temporary approach to the preceding vehicle, for example, when changing to the left lane is not yet possible. Even under these conditions, it is expedient to deactivate the tracking function briefly, in view of the impending lane change.
In every case, the transition between active and inactive phases of the automatic tracking function should be designed to be soft, in order to avoid abrupt interventions in the steering, and so that the driver is not irritated by a sudden change in the anti-torque moment noticeable at the steering wheel.
In the known cruise control and ACC systems, the possibility generally exists of briefly disabling the regulation by operating the gas pedal, so that the vehicle accelerates beyond the set setpoint speed. When the gas pedal is released again, the regulation automatically takes over again as soon as the vehicle""s speed has declined to the setpoint value. For reasons of consistency, it is expedient, under these conditions, also temporarily to disable the automatic tracking function together with the cruise control, and then to let it start up again synchronously with the cruise control. The driver will make use of the possibility of xe2x80x9cflooringxe2x80x9d the gas pedal especially when he wants to prepare for a passing procedure. It then makes sense to deactivate the tracking function. An exception may apply for the special case in which the optical sensor device recognizes that the vehicle is already in the left lane. In that case, the flooring of the gas pedal will then, as a rule, only have the effect of abbreviating the passing procedure in order to make it possible for the passed vehicle to cut into the left lane earlier. Under these conditions, it can be provided that the automatic tracking function remains active, by way of exception.